Commercial ceramic and glassware is often decorating by applying a pattern in colored ink on the surface of the substrate with screen printing, offset printing, or any other direct application technique. The glass is then baked at high temperatures to bond the indicia to the glass surface. This process, sometimes referred to as applied ceramic labeling (ACL), exhibits certain drawbacks. Often the ink compositions contain heavy metals and volatile organic solvents (VOC's). Both VOC's and heavy metals are undesirable from the environmental point of view. Second, ACL requires high temperature ovens for the baking step, which results in considerably energy usage and an increased potential for worker injury due to the high temperatures at which the process operates. Moreover, the high temperature ovens are expensive, cumbersome, pieces of equipment that require considerable floor space in factories.
On the other hand, use of radiation curable, particularly ultraviolet (UV) radiation curable, organic pigmented inks for decoration of glass and other vitreous materials is very desirable. Organic inks generally can be cured by exposure to radiation, such as UV radiation, thus obviating the need for high temperature baking. In addition, UV curable organic inks can be formulated to contain little or no VOC's or other nonaqueous solvents. One problem with organic inks is that they often do not exhibit adhesion equivalent to that obtained with ACL. Glass beverage and cosmetic containers must pass very stringent quality control tests, depending on the material which is sold in the container. For example, the decorative indicia on certain types of beverage bottles must be able to withstand pasteurization (exposure to water having a temperature of 70.degree. C. for one hour), or exposure to solutions of caustic base for extended periods of time at elevated temperatures.
Thus, there is a continuing effort to formulate radiation curable inks and utilize decorating methods which provide decorative indicia having durability and adhesion equivalent to that of ACL.
An object of the invention is to provide a composition to be used for pre-treating vitreous articles prior to application of radiation curable inks to cause the inks to exhibit improved durability and adhesion.
An object of the invention is to provide a method for pre-treating vitreous articles with a composition which will cause the radiation curable inks subsequently applied to to the article, to exhibit improved adhesion and durability.
An object of the invention is to provide a method for decorating glass and other vitreous articles with radiation curable ink compositions which exhibit improved adhesion and durability.